More from WebMD

March 3, 2011 -- Despite some previous research casting doubt on the value of physical activity for the knees, a new study says it’s beneficial for knee joint health.

Researchers in Australia say although it’s true that exercise has been linked to bony spurs called osteophytes, physical activity in general is good for the knees.

“Several studies have already examined the impact of physical activity on the knee as a whole, but none [has] looked at the effect of physical activity on individual parts of the knee,” Flavia Cicuttini, PhD, one of the researchers, says in a statement.

Cicuttini, of the Baker Heart Research Institute and Monash University in Melbourne, says “exercise affects each part of the knee differently, which helps explain why there have been conflicting reports for so long.”

Study Based on Data for Nearly 10,000 People

The research team, led by Cicuttini and Donna Urquhart, PhD, also of Monash University, examined data from 28 studies containing information on 9,737 people from all over the world.

All the studies examined the relationship between physical activity and knee osteoarthritis. Studies also included magnetic resonance imaging evidence of osteoarthritic knees when investigating disease progression, or healthy knees when researching disease incidence.

The researchers conclude that although exercise is linked to osteophytes, the study turned up no detrimental changes to joint space, the place where cartilage is housed.

Indeed, the scientists found beneficial effects of physical activity on cartilage integrity, and fewer defects.

“These findings are significant, as they suggest that osteophytes, in the absence of cartilage damage, may just be a functional adaptation to mechanical stimuli,” Urquhart says in the statement.

Osteoarthritis Affects 27 Million Americans

Osteoarthritis is a degenerative joint disease that attacks cartilage and underlying bone and often preys on the knees, hips, and hands. The disease affects 27 million Americans and is the leading cause of disability in non-institutionalized adults.

The researchers did not examine correlations between various forms of exercise, such as jogging and osteoarthritis or tennis and the disease.

Some of the studies used in their analysis examined knees of athletes, including soccer players, long-distance runners, and weight lifters.

“If all studies in the review were collectively examined, we would conclude that there is conflicting evidence for the relationship between physical activity and knee [osteoarthritis],” the authors write. “However, if we consider the relationship between physical activity and individual joint structures, we conclude that:”

There is strong evidence that there is a positive relationship between osteophytes and physical activity.

There is strong evidence that there is no relationship between joint space narrowing and physical activity.

There is limited evidence that there is a positive relationship between cartilage volume and physical activity.

There is strong evidence that there is an inverse relationship between cartilage defects and physical activity.

“These findings highlight the need to examine the effect of physical activity on individual structures of the knee joint rather than the joint as a whole,” the authors conclude. “Moreover, these findings suggest that physical activity may not have a detrimental effect on the knee joint, but may be beneficial to joint health.”

The study is published in Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine.